The present invention relates to Czochralski crystal growth devices, and more particularly, to an apparatus for reduction of vibration adverse to using such devices.
Metal single crystals can be prepared through controlled solidification. Although many single crystals grown without constraint tend to exhibit regular external faces, metal single crystals grown in a container conform to the shape of the container, if it is simple. Single crystals can be grown in several ways. In one method, a crucible containing the liquid is withdrawn at a fixed, slow rate from a furnace. Of the several grains formed at the pointed end of the crucible, only the most favorably oriented one survives to produce the single crystal. In a variation of this method, only a fraction of the material is molten at any one time, and this molten zone is moved slowly from one end of the material to the other, with a single crystal resulting as above. Such a molten zone can be achieved by a concentrated heat source in the form of an external electrical induction coil or an electrical resistance heating coil. In either of the above techniques, a small single crystal seed, which is kept solid at one end of the crucible, may be utilized to achieve a specific crystallographic orientation of the single crystal prepared.
Another widely used technique is that of crystal pulling. The material is melted in a crucible and held at a controlled temperature, and a small single crystal seed is brought into contact with the melt. As the seed is slowly withdrawn and rotated simultaneously, a single crystal grows. The diameter of the resulting single crystal is controlled by varying the melt temperature and/or the pulling rate. Although a holder is used for the seed, the crystal-liquid interface is unconstrained.
One problem with the above crystal pulling technique, particularly in Czochralski crystal pulling devices, is that rotation of the crystal requires mechanical linkage between a motor and the shaft to which the seed is attached. This linkage typically includes gear-type coupling, wherein gear teeth chatter and random vibration are experienced. This impacts upon the quality of the grown crystal.
Hence, it is the object of this invention to reduce the teeth chatter and vibration experienced in Czochralski crystal pulling devices.